1. Field Of The Invention
This invention relates to semiconductor electronic devices and circuits such as integral electronic circuitry and more particularly to an improved apparatus and method for creating wide-bandgap semiconductor electronic devices and circuits with laser radiation.
2. Background Of The Invention
Certain ceramics, such as silicon carbide (SiC) and aluminum nitride (AlN), are known to exhibit electrical properties ranging from insulating to semiconducting to conducting, as discussed in U.S. Pat. No. 5,145,741 issued Sep. 8, 1992, entitled“Converting Ceramic Materials to Electrical Conductors and Semiconductors” issued to Nathaniel R. Quick, and U.S. Pat. No. 5,391,841 issued Feb. 21, 1995, entitled “Laser Processed Coatings on Electronic Circuit Substrates” issued to Nathaniel R. Quick. The wide-bandgap semiconductor phases of these ceramics and other wide-bandgap semiconductors including diamond, are used to create devices such as conductive tabs, interconnects, vias, wiring patterns, resistors, capacitors, semiconductor devices and the like electronic components by laser synthesis on the surfaces and within the body of such wide-bandgap semiconductor to thereby eliminate photolithography processes which require numerous steps and generate undesirable chemical pollutants when processing such traditional electronic devices, components and circuitry.
As is well known alumina (Al2O3) dominates the dielectric market as an integrating substrate or device carrier in electronics packaging. BN, AlN, SiC and diamond are also of interest, due to their Thermal Coefficient of Expansion (TCE) and for their dielectric constant and higher thermal conductivity than that of Al2O3. SiC, AlN, BN, GaN and diamond also exhibit a wide-band gap and chemical resistance; they exhibit semiconducting to insulating properties. These properties are of substantial interest for new high temperature, approaching 1000° C. and aggressive environment applications, particularly where high integrated circuit packing densities are required. In the prior art, metallization methods, including dry-film imaging and screen printing have been used for the production of conductive patterns on alumina, however, metal compatibility with the newer high thermal conductivity ceramic materials such as AlN and SIC, have not completely solved. Copper and silver paste exhibits a TCE mismatch aggravated by high temperatures as well as being subject to oxidation that increases their resistivity. In particular, bonding of copper to AlN has proved to be nontrivial. alumina or stoichiometric aluminum oxynitride (AlON) coatings must be developed on the AlN surface through passivation processes. These passivation processes have poor reproducibility. Thus, the direct laser synthesis of conductors in AlN, SiC and diamond substrates appears to provide solutions to this long standing prior art problem with regard to metallization and for more simple processing techniques for creating devices and circuitry that are compatible with selected ceramic substrates, while satisfying the need for higher temperature, aggressive environment, and higher density integrated circuit packaging applications.